In digital television broadcasting, not only a broadcasting service of television programs, bus also a service called data broadcasting is realized (see, for example, Patent Literature 1).
Conventional data broadcasting is used, for example, to display information not directly related to a television program being viewed such as news, weather forecasts, and traffic information or to display information (casts, the story and so on) related to a television program being viewed.
Further, in conventional data broadcasting, displaying information (information about humans, things, shops or the like currently on the screen) synchronized with the progress of the television program being viewed is realized, though not frequently implemented.
Regarding data broadcasting in the future, a service (hereinafter, called a program progress synchronization information service) that displays information synchronized with the progress of the television program being viewed is demanded to be enriched (increased implementation frequency).